Methods of forming casts



United States Patent "ice 3,148,679 METHODS OF FORMING CASTS Harold L. Witcher, Perry, Okla. N0 Drawing. Filed June 14, 1962, Ser. No. 202,381 5 Claims. (Cl. 128-90) This invention relates generally to methods useful in forming relatively rigid surgical dressings more commonly referred to as casts. More particularly, it relates to methods of forming relatively rigid surgical dressings from synthetic materials.

Probably the most widely known method heretofore used to form casts has involved the use of plaster. In this method, a cloth sock is placed over the skin and a gauge-like material that has been impregnated with plaster is wetted to dissolve the plaster, and wrapped around the sock. Additional plaster may then be applied with another sock placed over the plaster. Subsequently, an additional amount of plaster is applied to finish the cast. Several distinct disadvantages adhere in the use and formation of plaster casts. They are very heavy and cumbersome, particularly when used on very young children or on the aged. They are subject to being broken or cracked rather easily. They absorb moisture and become soiled quickly. During the formation of the casts, the process is messy and in addition considerable heat is generated as the plaster dehydrates, resulting in a measure of discomfort to the patient.

More recently, some casts have been formed from fibre-glass combined with a resin. While casts formed of these materials overcome some of the disadvantages of plaster, they are diflicult to form and are relatively expensive.

It is therefore one object of this invention to provide an improved method for theh formation of a cast.

Another object of this invention is to provide an improved method for the formation of a cast that results in a light-weight, rigid, Water-impervious cast.

A further object of this invention is to provide an improved method for the formation of a cast that is simple to perform and results in no discomfort to the patient.

These, other, and further objects and advantages of the invention will become more apparent as the following description proceeds.

This invention contemplates the formation of a cast which involves placing a cloth-like material in contact with an expanded polystyrene which has been reduced to a plastic state and wrapping the prepared injured area with the cloth and polystyrene to a suflicient thickness to provide the desired support and then permitting the material to harden.

The process of this invention may be performed by several alternative procedures. The preferred method is to prepare several relatively long (as compared to their width) bags containing the polystyrene. The bags used may be closed on all edges if desired, but they should be so formed as to contain the polystyrene. They may be made of virtually any cloth, but the preferred material is either crinoline or gauze.

The polystyrene, which is placed in the bags dry, is preferably in a ground expanded form. Other forms of expanded polystyrene will perform satisfactorily, but the large amount of surface area in the ground condition aids in the rate of reduction of the polystyrene.

When a cast is to be formed, the injured area is prepared, i.e., the bone set or other conditions corrected, and a sock is placed over the area if applicable. Once the area is prepared, the bags containing polystyrene are dipped into acetone, which reduces the polystyrene to a very plastic consistency. The bag is then removed from the acetone and wrapped about the injured area. After 3,148,679. Patented Sept. 15, 1964 the polystyrene is contacted by the reducing agent, it permeates the cloth used for the bag. Successive wraps or layers of the bags adhere to each other due to the permeation of the polystyrene, thus forming virtually a unitary plastic cast reinforced by the cloth. Within approximately thirty to forty-five minutes the cast will be completely hardened, and it is important to note that during the hardening phase no heat is generated in the cast.

It should be pointed out that while acetone is the preferred agent, almost any of the petroleum derivatives will perform to some degree. Another substance that works equally as well as acetone is ether.

Briefly summarizing the preferred form of practicing the process, it includes:

(1) Preparing the bags containing ground expanded polystyrene.

( 2) Immersing the bags in acetone.

(3) Wrapping the bags in such a manner as to form the desired shape and size of cast.

Some injuries, such as a broken bone in the arm or leg, lend themselves to the use of a splint to give additional support to the cast. A splint can be formed from the bags by following the above-outlined procedure, except that a straight splint (or one matching the affected area) would be formed instead of step (3). The bags would then be wrapped around the splint and the arm or leg to form the completed cast.

Many alternatives to the above procedure are readily apparent. The bags or whatever form of cloth receptacle is used to contain the polystyrene do not necessarily need to be immersed as set forth in (2) above. When the ground form of polystyrene is used, the bags can simply be sprayed with the reducing agent. The requirement is that the polystyrene be reduced to a highly pliable or plastic condition so that the cast can be formed.

Another alternative procedure that works very nearly as well as the preferred process is to either dip or spray the cloth with the reducing agent then immerse the cloth in the ground polystyrene. The polystyrene which comes into contact with the saturated cloth adheres thereto and is reduced to the desired plastic consistency. The cast is then formed as described hereinbefore.

From the foregoing, it is believed obvious that the method of this invention results in a cast that is light in weight, easy and clean in its application, water impervious, stronger, and provides an additional benefit not quite so obvious, that is, it is comparable to plaster casts in cost.

The above description is by Way of example only and it is believed that many changes and modifications may be made thereto without departing from the spirit of the invention or from the scope of the annexed claims.

What I claim is:

1. In a process for forming a relatively rigid surgical cast, the steps of 1) holding a cloth and a loose aggregate of ground expanded polystyrene in contact,

(2) placing said cloth and polystyrene in intimate contact with an agent adapted to reduce said polystyrene to a readily formable plastic state, whereby a pliable composite sheet is formed therefrom,

(3) shaping said composite sheet into the desired form,

and

(4) evaporating said agent until said composite sheet will retain the desired shape.

2. In a process for forming a relatively rigid surgical cast, the steps of (1) contacting a cloth with an agent adapted to reduce a ground expanded polystyrene to a readily formable plastic state,

(2) placing the treated cloth in contact with a loose aggregate of ground expanded polystyrene, whereby a pliable composite sheet is formed,

(3) shaping said composite sheet into the desired form,

and

(4) evaporating said agent until said composite sheet will retain the desired shape.

3. In a process for forming a relatively rigid surgical cast, the steps of (1) bringing a loose aggregate of ground eXpanded polystyrene into contact with an agent adapted to 10 reduce said polystyrene to a readily formable plastic state,

(2) placing a cloth in contact with said reduced polystyrene, whereby a pliable composite sheet is formed therefrom,

4 (3) shaping said composite sheet into the desired form,

and (4) evaporating said agent until said composite sheet will retain the desired shape. 4. The process of claim 1, wherein said agent is acetone.

5. The process of claim 1, wherein said agent is ether.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A PROCESS FOR FORMING A RELATIVELY RIGID SURGICAL CASE, THE STEPS OF (1) HOLDING A CLOTH AND A LOOSE AGGREGATE OF GROUND EXPANDED POLYSTYRENE IN CONTACT, (2) PLACING SAID CLOTH AND POLYSTYRENE IN INTIMATE CONTACT WITH AN AGENT ADAPTED TO REDUCE SAID POLYSTYRENE TO A READILY FORMABLE PLASTIC STATE, WHEREBY A PLIABLE COMPOSITE SHEET IS FORMED THEREFROM, (3) SHAPING SAID COMPOSITE SHEET INTO THE DESIRED FORM, AND (4) EVAPORATING SAID AGENT UNTIL SAID COMPOSITE SHEET WILL RETAIN THE DESIRED SHAPE. 